Live Sound/PA Buying Guide
(PA_Gear | Posted 2010-07-03)
So you need to get a PA system but you’re not too sure where to start. You go into your local music shop and he starts talking about ohms law, 3-way crossovers, and dispersion angles. You nod your head like you care and look for the closest fire exit for a quick escape.
The truth is, most people buying a PA for the first time know nothing about it and end up leaving the store over-budget and with things you really don’t need. I am going teach you everything you will need to know to go out and buy your first PA so give yourself a round-of-applause for picking the right place!
Here’s the deal…
A basic PA system will most likely include some microphones, a mixer, two main speakers, a few monitors, and all of the cables and stands in between. A large PA may include amplifiers, crossovers, processors such as EQ and compression, subwoofers, side washes, and so much more. How big or small you go is totally up to you and definitely relates to what you are going to be using it for.
The first question you need to ask your self is, “What do I need a PA for and what types of spaces will I be using it in?” Answering this will help you decide how many inputs, speakers, microphones, cables, and stands you will need. Once you figure this out, move on to the next section.
Picking out a Mixer
The mixer is “Command Center One” of your live sound spaceship and everything from monitor mixes to microphone gain will be controlled here. It is a large board with lots of knobs and buttons that will be re-routing and adjusting all of your audio signals. Each audio signal will be represented by a channel and each channel will have various capabilities such as gain control, EQ, aux sends, and a fader that controls mix level.
There are three main types of mixers known as powered, analog, and digital. Analog mixers have circuit boards designed to sound a certain way whereas digital mixers have sound processors that may emulate analog circuit boards. A powered mixer just means that it can send power to passive speakers but we’ll talk about that more later. Digital mixers can be great because you can store settings that are easily recalled for various gigs. There are advantages to each type and none is better than the other.
Also be aware of the difference between monitors and mains. Monitors are on stage facing the performers and are mixed through aux sends on your board. Depending on the capabilities of your mixer, you can send individual mixes to every person on stage. The main mix will be controlled by the faders on your mixer and will come out the speakers facing the audience.
Once you decide which type of mixer you want, you need to make sure that it can has all of the inputs and outputs that you will need. If you are mostly doing small coffee shop gigs with a few acoustic guitars and vocals then a 4-8channel mixer with 1-2 aux sends for monitors will be fine. If you plan on doing larger venues with multiple instruments you will want 16 or more inputs with at least 6 aux sends. You may also want inserts for outboard gear and in-depth channel EQ’s for more control.
Going back to the very beginning, I told you to think about the space you would be using your PA in. This is going to directly relate to which speakers you will want. As a general rule, coffee shop gigs, lectures, or small rooms will need speakers around 300-500 watts. Larger venues, outdoor performances, or party DJs will most likely want something around 500 watts and up.
There are two main types of speakers including active and passive. An active speaker will have an amplifier built in and will require nothing but some speaker cable to connect to your mixer and a plug. Passive speakers will need some sort of amplifier in line between it and the mixer so that it can be powered.
If you decide to go with passive speakers for your mains or monitors you will also need amplifiers for each. A good general rule for matching an amp with a speaker is to make sure that the amp can deliver 1 1/2 to 2 times what the speaker’s continuous IEC power rating is. You will also need to make sure that the ohms (resistance) match. This can get very confusing and if you have any questions feel free to contact me via the bottom of this page.
For larger applications you may also want multiple line-array speakers and probably subwoofers. In order to split the lows from the high’s, you will need a crossover which does just that. There are two-way and three-way crossovers and the only difference is that the three-way adds in the mids.
In order to pick up sounds on the stage, you will need microphones, Dynamic mics are great choices for PA because they are sturdy and typically made for being on stage. You will typically want to look for microphones that are unidirectional (only captures sound from the front) as getting to many sounds from the stage or monitors can create feedback. Shure SM58’s are great for vocals and Shure SM57’s are perfect for miking guitar, bass, and keyboard amps. A Shure Beta 52 is awesome on a kick drum and, again, the Shure SM57 will do well on snare and toms. Shure microphones are durable, dependable, and have stood the test of time. They are also relatively cheap and you’ll see them on the biggest stages with the hottest artists.
We have a great buying guide just for microphones here:
There are 5 billion types of signal processors out there but there are a few main categories that you should be aware of. None of these things are necessary but they are recommended and will make your PA the hottest PA in the tri-country area.
Reverberation is an effect that can make sounds appear as if they are bouncing off of multiple surfaces and adds depth and size to a mix. Reverb units will let you adjust things such as plate, room size, early reflections, and more. If you want to hear what reverb sounds like, go listen to any song Coldplay ever recorded. Reverb is great for molding mixes together and can really smooth out a vocal. It’s perfect for adding space to a mix.
Have you ever clapped your hands or screamed profanities in a big room? Remember when you stopped and it kept bouncing off the walls and then your third grade teacher heard and sent you home? This is called an echo, which is essentially delay. When the original sound is made and then distinct repetitions of that sound come later and eventually go away, you’ve got delay. Delay can sound great on vocals or guitars but is typically not put on an entire mix.
A compressor takes a sound wave with lots of ups and downs and smoothes it out to a much more even level. It can reduce the difference between the softest and loudest sounds coming from an audio signal. Compressors have settings like ratio, attack, and release. Ratio relates to the amount of signals it receives versus the amount of signal it puts out. So for a 3:1 ratio the compressor will put out 1dB for every 3dB it receives. A limiter can protect your gear by limiting the sound that can pass through it at a certain level. If somebody on stage drops a microphone, the limiter will cut off that peak in the system which normally could blow a speaker or someone’s ears.
Equalizers, or EQs, allow you to cut or boost audio signals at a specific frequency. They can help you get rid of feedback in monitors, cut back a frequency that is too dominant, or boost a frequency that is lacking. Most mixers will have EQs build in for each individual track but it is a good idea to have individual EQs for each of your mains and monitors to have more control over your mixes.
Now you have all of your great new gear but no way to connect it all together and set it up! You are going to need speaker stands, XLRs, a snake, speaker cable, power strips, extension chords, a table for your mixer, and many other things that may come along. A snake can have anywhere from 4+ inputs and runs as a single line from the stage to your mixer. It will eliminate a lot of clutter. Also, 1/4" speaker cable is not the same as 1/4" instrument cable. Be sure to talk to your local music store and they’ll help you find the right ones.
It is always a good idea to keep extras of everything when using your PA for a gig. As Murphy’s Law states, anything that can go wrong, will go wrong. This doesn’t apply anywhere better than live sound. Keep a box full of extra XLRs, 1/4" cables, adapters, power strips, tape, and anything else that could be stepped on, ripped, or broken.
Well there you have it. You are off to a great start on purchasing your new PA system. Welcome to the world of headaches and problem solving. You’ll become an expert at the process of elimination and you’ll start learning words your friends will make fun of you for knowing.